[DeTomaso] A/C condensor fan test results

[Mikael]

Hi Tom, one of the faces I remember from POCA FUN Rally...

" Any and all comments are welcome." Well I had an A/C issue in my
Longchamp, orig system but with new shaker compressor. It worked fine, but
cooling effect was not as it should be. That meant that in warm weather I
had the A/C knob turned to max, and while a lot better than nothing, not
really impressive. On a dusty parking lot on one of Charlie's European tours
I found that the heater cable was misaligned, so it couldn't turn off the
hot coolant all the way. I couldn't fix the cable bracket angle then and
there, but I could by hand turn off the water flow entirely. And from that
moment: Super A/C, have never had to run it max anymore, it cycles on and
off.

Pretty basic I know, but maybe...


Mikael

-----Oprindelig meddelelse-----
Fra: Tom Shinrock [mailto:tmshinro at aol.com] 
Sendt: 5. maj 2013 04:38
Til: detomaso at poca.com
Emne: [DeTomaso] A/C condensor fan test results

Those I met at the fun rally probably got bored/annoyed with my stories of
my air conditioner not being effective on my drive from Iowa to Phoenix
(believe me....I heard about it from Dena on the drive back).  I had the
system filled will R-12 before I left Iowa.  I put in a new rotary
compressor and drier last summer along with a high temp cut off switch.
Before that I never tried to get my A/C working.  I was pleased to find a
number of people that claimed to have effective A/C with rear mounted
condensers so I have hope that I can get mine to work.


Gil Mares and Les Gray went out of their way to look at my system and put me
in touch with some A/C experts in Phoenix.  To shorten a long story, when
Les looked at the system we found that the A/C worked in the parking lot
blowing 60 degree air with ambient temps around 100 in the car.   He didn't
see any bubbles in the drier site glass.  He also noted that I had original
hoses.  I called the experts that Gil had referred me to and gave them the
results of the parking lot test.  Their opinion was that no bubbles
indicated that the system was fully charged and the fact that  the A/C
worked in the parking lot but not on the highway suggested that the
condenser was not being taking enough heat out of the system which was
probably due to a underpowered fan and/or an ineffective condenser.


On the way home I would periodically turn on the air and find that it would
blow cool air for a very short time and then stop working.  On my last day
of driving I ran the A/C in the late morning before it got crazy hot and
found that the air actually worked for about an hour and a half before it
quit working.  During that stretch I heard a sound I've rarely heard; the
A/C relay clicking on and off.  This experience pushed me further to the
conclusion that my condenser wasn't pulling enough heat out of the system
and when it got hot enough my cut off switch was shutting down the
compressor.


I replaced my stock condenser fan with a new fangled one last summer
thinking it would be better.  Since then I've read many opinions that the
stock fan moved more air.  John Buckman described to me how he tested
various aftermarket fans using increasing amounts of cardboard at the
condenser grill to determine which fan provided the most suction to hold the
cardboard in place.  He said he did not conduct that test for the stock fan
however.


Feeling that my A/C would be more effective if I could move more air through
the condenser, I decided to perform the cardboard test to see how my
aftermarket fan compared to the stock fan.  Here's what I found:



With my aftermarket fan installed I cut a piece of cardboard the size of the
grill opening and turned the fan on via a battery charger and saw that the
fan sucked the cardboard and held it to the grill.   I then taped more and
more cardboard to this first piece of cardboard until the fan could no
longer provide enough suction to hold the mass of cardboard against the
grill.


I then removed the aftermarket fan and re-installed my stock fan (by the way
both fans had dense foam stuffed into the sides of the fan shroud to seal
the gap between the shroud and car body to prevent the fan from sucking any
air from inside the engine compartment).  I found the stock fan could easily
hold the mass of cardboard I ended up with when testing the aftermarket fan.
I then proceeded to add more and more cardboard until the stock fan could
not provide enough suction to hold the mass of cardboard to the grill.  Both
tests were performed with the tub out.


I don't have a scale small enough to weigh the different amounts of
cardboard to quantify the difference in weight but I did calculate the
equivalent area of card board that each fan could hold.  The aftermarket fan
held 677 square inches of cardboard and the stock fan held 782 square inches
(15.5% more).  So obviously I was not getting as much condenser cooling with
the aftermarket fan.


I then proceeded to test the A/C with the tub in.  I put a temperature probe
in the dash vent which indicated 70 degrees ambient.  I turned the A/C on
saw that the vent air temperature was an indicated 25 degrees.  I won't
really know how good it performs until we get some hot weather around here.



I heard a lot of people talk about parallel flow condensers.  I know I don't
have a stock condenser but I don't really know what kind came with the car.
When I was switching condenser fans, I took a closer look at it and I'm
wondering if it is a parallel flow design.   I took some pictures of it to
see if someone can tell me what I have.
http://poca.com/index.php/gallery/?g2_itemId=40199


Any and all comments are welcome.


Tom
#5186